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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/390223051): Remove C-library calls to fix the errors.
#pragma allow_unsafe_libc_calls
#endif
#include "base/test/file_path_reparse_point_win.h"
#include <windows.h>
#include <winioctl.h>
#include <utility>
namespace base::test {
namespace {
// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/ns-ntifs-_reparse_data_buffer
// This struct should be available in the windows sdk in ntifs.h, but the
// chromium builders do not find this file.
typedef struct _REPARSE_DATA_BUFFER {
ULONG ReparseTag;
USHORT ReparseDataLength;
USHORT Reserved;
union {
struct {
USHORT SubstituteNameOffset;
USHORT SubstituteNameLength;
USHORT PrintNameOffset;
USHORT PrintNameLength;
ULONG Flags;
WCHAR PathBuffer[1];
} SymbolicLinkReparseBuffer;
struct {
USHORT SubstituteNameOffset;
USHORT SubstituteNameLength;
USHORT PrintNameOffset;
USHORT PrintNameLength;
WCHAR PathBuffer[1];
} MountPointReparseBuffer;
struct {
UCHAR DataBuffer[1];
} GenericReparseBuffer;
};
} REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;
} // namespace
std::optional<base::test::FilePathReparsePoint> FilePathReparsePoint::Create(
const FilePath& source,
const FilePath& target) {
auto reparse_point = base::test::FilePathReparsePoint(source, target);
if (!reparse_point.IsValid()) {
return std::nullopt;
}
return std::move(reparse_point);
}
FilePathReparsePoint::FilePathReparsePoint(FilePathReparsePoint&& other)
: dir_(std::move(other.dir_)),
created_(std::exchange(other.created_, false)) {}
FilePathReparsePoint& FilePathReparsePoint::operator=(
FilePathReparsePoint&& other) {
dir_ = std::move(other.dir_);
created_ = std::exchange(other.created_, false);
return *this;
}
FilePathReparsePoint::~FilePathReparsePoint() {
if (created_) {
DeleteReparsePoint(dir_.get());
}
}
// Creates a reparse point from |source| (an empty directory) to |target|.
FilePathReparsePoint::FilePathReparsePoint(const FilePath& source,
const FilePath& target) {
dir_.Set(
::CreateFile(source.value().c_str(), GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
OPEN_EXISTING,
FILE_FLAG_BACKUP_SEMANTICS, // Needed to open a directory.
NULL));
created_ = dir_.is_valid() && SetReparsePoint(dir_.get(), target);
}
// Sets a reparse point. |source| will now point to |target|. Returns true if
// the call succeeds, false otherwise.
bool FilePathReparsePoint::SetReparsePoint(HANDLE source,
const FilePath& target_path) {
std::wstring kPathPrefix = FILE_PATH_LITERAL("\\??\\");
std::wstring target_str;
// The juction will not work if the target path does not start with \??\ .
if (kPathPrefix != target_path.value().substr(0, kPathPrefix.size())) {
target_str += kPathPrefix;
}
target_str += target_path.value();
const wchar_t* target = target_str.c_str();
USHORT size_target = static_cast<USHORT>(wcslen(target)) * sizeof(target[0]);
char buffer[2000] = {};
DWORD returned;
REPARSE_DATA_BUFFER* data = reinterpret_cast<REPARSE_DATA_BUFFER*>(buffer);
data->ReparseTag = 0xa0000003;
memcpy(data->MountPointReparseBuffer.PathBuffer, target, size_target + 2);
data->MountPointReparseBuffer.SubstituteNameLength = size_target;
data->MountPointReparseBuffer.PrintNameOffset = size_target + 2;
data->ReparseDataLength = size_target + 4 + 8;
int data_size = data->ReparseDataLength + 8;
if (!DeviceIoControl(source, FSCTL_SET_REPARSE_POINT, &buffer, data_size,
NULL, 0, &returned, NULL)) {
return false;
}
return true;
}
// Delete the reparse point referenced by |source|. Returns true if the call
// succeeds, false otherwise.
bool FilePathReparsePoint::DeleteReparsePoint(HANDLE source) {
DWORD returned;
REPARSE_DATA_BUFFER data = {0};
data.ReparseTag = 0xa0000003;
if (!DeviceIoControl(source, FSCTL_DELETE_REPARSE_POINT, &data, 8, NULL, 0,
&returned, NULL)) {
return false;
}
return true;
}
} // namespace base::test
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